facboy

hi all,

my car seems to have a misfire or something at WOT around 4500-5000rpm. it doesn't always happen, just some of the time. it feels a bit like hitting the overboost protection, but without the attendant behaviour afterwards (only boosting to 1.2bar for a minute).

i'm running guru chips at 18psi, with an accuboost (and the 3 bar fpr). car is an 89.

any thoughts?

cheers,

chris.

mdex

I had a vac leak leading into the FPR that caused the same thing.

Danno

It might be too rich of a air-fuel mixture in that range. I usually add a little extra fuel in the 4000-5000rpm range when boost is at is maximum. From ShockM's chart a couple weeks ago, his '89 18psi chips had a little too much fuel there. Make sure you have selected the 18psi maps on the chips, otherwise, you might be running with the 15psi maps. Did I send you the latest instructions with your upgraded chip?

facboy

um, no. how can i tell which map i'm running? i don't have the rcp or the ia plugged in, so i assume that means i'm running the usa map. is that the 18psi map?

it doesn't do it all the time though, and it's quite a violent 'stumble' (it only jerks once and then i back off) - feels like hitting the rev limiter, or the stock overboost protection.

Tom M'Guinn

If it is not a chip issue, spark plug wires are often the cause of high-load missing in turbo cars. I've had bad wires cause this in my rx7tt and the 951. I wonder if the extra heat from the turbo contributes to short wire life. The rx7 wires went bad at 30k miles!

Danno

Yeah, try narrowing your spark-plug gaps down to 0,5 to 0,6mm.